This invention relates to a color cathode-ray tube (CRT) and, more particularly to the manufacturing of a luminescent screen assembly using a filming composition comprising an acrylic polymer dissolved in a solvent mixture of one or more high-volatility solvents combined with one or more low-volatility solvents.
A color cathode-ray tube (CRT) typically includes an electron gun, an aperture mask, and a screen. The aperture mask is interposed between the electron gun and the screen. The screen is located on an inner surface of a faceplate panel of the CRT tube. The aperture mask functions to direct electron beams generated in the electron gun toward appropriate color-emitting phosphors on the screen of the CRT tube.
The screen may be a luminescent screen. Luminescent screens typically comprise an array of three different color-emitting phosphors (e.g., green, blue, and red) formed thereon.
Luminescent screens may be formed using an electrophotographic screening (EPS) process. In EPS processes, an organic photoconductive (OPC) layer is sprayed over an organic conductive (OC) layer, formed on an interior surface of a CRT faceplate panel having a light-absorbing material formed on portions thereof. Color-emitting phosphors are sequentially deposited on portions of the OPC layer and fixed with an appropriate fixative to secure the phosphors to the OPC layer. Thereafter, the luminescent screen is further processed when a layer, or a film, of a material composition is applied over the fixed phosphors to provide a smooth surface.
The filming composition is applied over the fixed phosphors using an electrostatic spraying process within an enclosed electrostatic spray system. In an electrostatic spraying process, one or more electrostatic guns produce an aerosol of charged droplets of the filming composition, which is spray-deposited onto the fixed phosphor of the interior surface of the CRT faceplate panel to provide a smooth surface onto which an aluminum layer is deposited. One drawback with electrostatic spraying processes is that the aerosol of droplets may splatter on the components of the spray system forming film deposits on interior surfaces thereof. These film deposits provide a potential source of particles, which can potentially be deposited on the fixed phosphor surface during the filming process, resulting in undesirable screen blemishes.
Thus, a need exists for a suitable filming composition that overcomes the above-mentioned drawbacks.
The present invention relates to a method of manufacturing a luminescent screen assembly for a color cathode-ray tube (CRT). The luminescent screen assembly is formed on an interior surface of a faceplate panel of the CRT. The luminescent screen assembly includes an organic conductive (OC) layer overcoated with an organic photoconductive (OPC) layer. Different color-emitting phosphors are sequentially deposited over portions of the OPC layer and fixed with an appropriate fixative to secure the phosphors to the OPC layer.
Thereafter, the luminescent screen is completed when a filming composition is electrostatically sprayed over the fixed phosphors. The filming composition comprises an acrylic polymer dissolved in a solvent mixture of one or more high-volatility solvents combined with one or more low-volatility solvents.